Search

Background: The size effect and deformation instability exhibited by materials at the micro- and nano-scale constrain the development and application of miniaturized devices. Introducing different defects in materials through different technical means to improve the deformation stability of materials has been the main research point of micro- and nano mechanics. Objective: This paper presents a novel strategy to completely eliminate the instability of microscopic deformations by the introduction of high-density precipitates in aluminum alloys by means of suitable heat treatment. Methods: A suitable heat treatment is used to introduce a high density of precipitates in the 7075 aluminum alloy. Using the Focused Ion Beam technique and in situ micropillar compression tests, micron-sized single-crystal micropillars were fabricated and the size dependence of the strength and strain-hardening behavior of 7075 aluminum alloy was systematically analyzed. Results: Compared with precipitate-free Al–Mg alloy micropillars, the micropillars fabricated from 7075 aluminum alloy exhibited more stable deformation behavior, predominantly due to the impediment of dislocation motion by precipitates. The power-law exponent for yield strength relative to pillar size was determined to approach a near-zero value, indicating a negligible dependency of yield strength on specimen size. Similarly, the smaller the size of micropillar, the higher the hardening rate, which can be rationalized by exhaustion hardening. Conclusions: The proposed method can eliminate the size effect of materials with pillar size above 0.5 μm and leads to a stabilization in deformation behavior. These are advantageous for the application of micro- and nano-sized components in advanced engineering systems. [ABSTRACT FROM AUTHOR]

The preparation and realization of highly reliable thermal barrier coatings (TBCs) on the internal surface of complex cavities is a bottleneck problem. Traditional coating methods are difficult to deposit and fulfil service requirements. In this study, a novel structure of YSZ and Ce-doped YSZ (CeYSZ) TBCs was prepared by a newly cathode plasma electrolytic deposition (CPED) technology. The results suggested that both the CPED-YSZ and CPED-CeYSZ coatings exhibited porous cross-linked dendritic structures. Because Ce doping significantly improved the phase stability of tetragonal structure and enhanced thermal insulation temperature during a burner-rig test at 1300 °C, resulting in a threefold increase in the thermal cycling life of the CPED-CeYSZ coating compared to the CPED-YSZ coating. This work provided a new strategy for tailoring multiple rare-earth principal components of high-performance TBCs and depositing them on the inner surface of complex cavities with high aspect ratios. [ABSTRACT FROM AUTHOR]

The reliability of high-voltage circuit breakers (HVCBs) depends critically on the dynamic characteristics of their hydraulic operating mechanisms (OMs). However, previous analyses have been limited to discrete components due to the lack of models capturing multi-physics couplings. This paper proposes a novel co-simulation approach for hydraulic OMs that enables system-level analysis. Specifically, the hydraulic system is modelled using the lumped parameter method, and the transmission mechanism is modelled via finite element analysis. The subsystem models exchange inputs and outputs through shared memory, realizing coupling without compromising simulation performance. Experiments on a 550 kV HVCB validate that the model accurately captures OM transient responses. The co-simulation framework has diverse capabilities, including predicting dynamics under varied operating parameters and quantifying stress distributions and response evolution patterns. Overall, this paper proposes an advanced multi-physics analysis capability for hydraulic OMs to support reliabilityoriented design and optimization. [ABSTRACT FROM AUTHOR]

Power parameters are of importance to determine the microstructure and property of coatings deposited by cathode plasma electrolytic deposition (CPED). In the present study, the effect of power parameters including voltage and duty cycle on the microstructure and anti-corrosion property of zirconia (ZrO 2) CPED-coatings was investigated. The results suggested that the as-deposited coatings consisted of t -ZrO 2 and m -ZrO 2 , while the content of t -ZrO 2 exceeded 50 %. The content of t -ZrO 2 increased with the increase of voltage and decreased with the increase of duty cycle, reaching a maximum of 89.9 %. In addition, as the voltage and duty cycle increased, the porosity of the coating increased from 3.7 % to 15.5 %. Due to the high t -ZrO 2 content, high thickness and relatively dense structure, the coatings deposited at 250 V had a superior corrosion resistance in 3.5 wt% NaCl solution. This work will provide a guideline for tailoring high performance ZrO 2 CPED-coatings. [ABSTRACT FROM AUTHOR]

We have conducted a detailed study of single-pulse emission from PSR J1722−3207, which was observed at 1369 MHz using the Parkes 64 m radio telescope. PSR J1722−3207 has an asymmetric two-component mean pulse profile. We find that the brighter leading component exhibits a periodic phase-stationary nondrift amplitude modulation while the trailing component remains unchanged. As a result of this, this pulsar switches between a strong state and a weak emission state periodically. Spectral analysis of the fluctuations showed that the modulation period is very short (∼2.0 s or 20 P), where P is the rotation period of the pulsar. The polarization properties of the strong and weak states were investigated. The swings in the position angle of the two states are similar, suggesting that their basic emission geometry is the same. At present, it is difficult to explain the periodic mode-changing phenomenon observed in this pulsar with existing subpulse drifting models. [ABSTRACT FROM AUTHOR]

In this paper, the acoustic signal of the underwater explosion was taken as the main research object, and the mechanical and acoustic characteristics of the underwater explosion were studied by combining theoretical research with simulation, the propagation law of shock wave and the acoustic characteristics of explosion signal with different explosion depth and charge were obtained. The results show that the underwater explosion has strong acoustic power, high sound pressure level, wide frequency coverage of explosion acoustic signal. In low frequency band, the acoustic power level decays rapidly with the increase of frequency, and its acoustic energy is very high; in higher frequency band, the acoustic power level decays slowly, and its sound energy is relatively low; bubble pulsation has a great influence on the energy distribution of acoustic power level, and the more bubble pulsation times, the greater the proportion of low-frequency energy. The research results of this article can provide a theoretical basis for the research of fuze anti-interference. [ABSTRACT FROM AUTHOR]

We investigated the clinical outcomes of breast cancer brain metastases (BCBMs) treated with stereotactic radiosurgery (SRS) with or without systemic metastasis. We retrospectively reviewed patients who underwent SRS to BCBMs from 2005-2020 from a prospectively maintained database. Patients were stratified by BCBMs with or without systemic metastasis on the date of SRS. The Kaplan-Meier method was used to calculate overall survival (OS), central nervous system progression free survival (CNS-PFS), and distant intracranial control (DIC) from the date of SRS. Prognostic variables were assessed using the Cox proportional hazards model. We identified 223 patients who underwent SRS to 819 BCBMs. Of the 223 patients, 179 (80%) had systemic metastasis with 722 BCBMs, while 44 (20%) had no systemic metastasis with 97 BCBMs on the date of SRS. No differences were noted in patients with or without systemic metastases with regards to histology (P = 0.93), subtype (P = 0.48), age (P = 0.32), or Karnofsky Performance Status (KPS) (P = 0.66). There was a trend towards patients without systemic metastases having fewer brain metastases (P = 0.07) and undergoing surgical resection of brain metastases (P <0.0001). Median follow-up from the date of SRS was 76.4 months (range = 1.3-131.0). In patients with or without systemic metastasis on the date of SRS, the median OS was 22 months (95% CI = 18.3-25.66) and 38.1 months (95% CI = 24.77-46.73) (P = 0.01), respectively. The median CNS-PFS was 8.6 months (95% CI = 7.83-10.37) and 13.0 months (95% CI = 6.93-19.1) (P = 0.078), respectively. The median DIC was 10.0 months (range = 8.4-11.7) and 13.7 months (range = 8.9-31.2) (P = 0.03), respectively. On univariate analysis, absence of systemic metastasis on the date of SRS was associated with improved survival (HR = 0.60, 95% CI = 0.41-0.89, P = 0.01). On multivariate analysis, the HER2 positive subtype was associated with improved survival (adjusted HR = 1.9, 95% CI = 1.04-3.29, P = 0.04). Of the 44 patients who had no systemic metastasis on the date of SRS, 29 patients (66%) received systemic treatment after SRS including CDK 4/6 inhibitors (n = 2; 7%), anti-PD-1 therapy (n = 4; 14%), chemotherapy (n = 7; 29%), HER2 targeted therapy (n = 12; 41%), and endocrine therapy (n = 8; 28%). A total of 14 of these 44 patients (31.8%) eventually developed systemic metastasis after SRS, most commonly to the bone (33%), liver (33%) and lung (27%). BCBMs without systemic metastasis is a rare presentation but after SRS these patients were noted to have improved OS and DIC. Further investigation into the biology of patients with brain only breast metastatic disease is warranted. [ABSTRACT FROM AUTHOR]

Wet‐assembly hybrid bonded/bolted (WHBB) joint is a kind of sealing fastener that contains sealant both in bolt‐hole clearance and between CFRP laminates, which is increasingly applied in composite aircraft fuel tanks. As the guarantee of tensile strength and sealing performance, the thickness and interface characteristics of bolt‐hole sealant layer are investigated by a newly developed comprehensive evaluation method in this paper. The results indicate that the tensile strength of WHBB joint is positively correlated with the bolt‐hole clearance. As for the sealing property of WHBB joints, the leakage rates of WHBB joints with bolt‐hole adhesive layer (0.01, 0.03 and 0.05 mm) is three orders of magnitude less than that of joints with 0 mm adhesive layer. Moreover, the rising slope of leakage rates of the WHBB joints decreases with the increase of bolt‐hole clearance under tensile fatigue loads, which means the WHBB joint with higher bolt‐hole clearance shows better tensile fatigue resistance. The micro‐morphology of bolt‐hole interface indicates that the sealing property of WHBB joints is increased significantly due to the effectively enhanced interface behavior. [ABSTRACT FROM AUTHOR]

To investigate the association between intracranial plaque characteristics and high-sensitivity C-reactive protein (hs-CRP) levels, and their combined effects on the occurrence of acute cerebral infarction (ACI). One hundred and forty-three patients with recent ischaemic events in the territory of middle cerebral artery or basilar artery were enrolled and divided into the ACI group (n= 93) and non-ACI group (n= 50) according to clinical data and diffusion-weighting imaging (DWI) results. All recruited patients underwent high-resolution magnetic resonance imaging (MRI) to assess intracranial plaque characteristics, including plaque enhancement, standardised wall index, stenosis ratio, T1 hyperintense component, remodelling pattern, plaque area, plaque burden, and maximum wall thickness. hs-CRP levels were further grouped into the low group (<1 mg/l), the intermediate group (1–3 mg/l), and the high group (≥3 mg/l). Multivariate logistic regression and receiver operating characteristic curve were constructed to evaluate the association between intracranial plaque characteristics and hs-CRP levels, as well as their synergistic effects on determining the occurrence of ACI. High hs-CRP levels were associated with strong plaque enhancement (p< 0.001, odds ratio [OR] = 7.497). Strong plaque enhancement (p= 0.002, OR=2.109) and high hs-CRP levels (p= 0.009, OR=3.893) were independently associated with the occurrence of ACI after adjustments for sex, age, and other traditional atherosclerotic risk factors. The combination of hs-CRP levels and strong plaque enhancement provided incremental information to determine ACI with an AUC of 0.823, which was significantly higher than that of strong plaque enhancement (0.711) and hs-CRP levels (0.686), respectively. High hs-CRP levels were associated with strong plaque enhancement. The synergistic effects of hs-CRP levels and strong plaque enhancement provided incremental effects on the occurrence of ACI. • High hs-CRP levels are associated with strong intracranial plaque enhancement. • Combination of hs-CRP and strong plaque enhancement shows incremental effects on ACI. • Monitoring hs-CRP and plaque may contribute to ischemic stroke risk stratification. [ABSTRACT FROM AUTHOR]

To compare the accuracy of three-dimensional (3D) high-resolution (HR) magnetic resonance imaging (MRI), time-of-flight magnetic resonance angiography (TOF-MRA), contrast-enhanced magnetic resonance angiography (CE-MRA), and digital subtraction angiography (DSA) in measuring the degree of stenosis in intracranial atherosclerosis. All patients with intracranial artery ischaemic events underwent HR-MRI, TOF-MRA, and CE-MRA analysis, and some of these patients underwent DSA examination. The correlation between different methods for measuring the degree of lumen stenosis was analysed. The accuracy of HR-MRI, TOF-MRA, and CE-MRA was evaluated and compared with that of DSA. A total of 189 arterial stenoses were identified in 93 patients. Of these, 72 patients with 142 arterial stenoses underwent DSA examination. A very strong correlation between HR-MRI and CE-MRA measurements was shown (r= 0.839, p< 0.0001). The correlation between HR-MRI and TOF-MRA measurements was strong (r= 0.720, p< 0.0001). A very strong correlation between HR-MRI and DSA measurements was found (r= 0.864, p< 0.0001), and a similar correlation was observed between CE-MRA, and DSA measurements (r= 0.843, p< 0.0001). The correlation between TOF-MRA and DSA measurements was strong (r= 0.686, p< 0.0001). There was substantial agreement between HR-MRI and DSA measurements (K = 0.772) and between CE-MRA, and DSA measurements (K = 0.734) that was slightly higher than the agreement between TOF-MRA and DSA measurements (K = 0.636). HR-MRI can accurately measure stenosis (especially for moderate and severe stenosis) in intracranial atherosclerosis by direct visualisation of the vessel lumen and steno-occlusive plaque. • Very strong correlation between 3D HR-MRI and CE-MRA in measuring lumen stenosis. • Strong correlation between 3D HR-MRI and TOF-MRA in measuring lumen stenosis. • Substantial agreement between 3D HR-MRI and DSA for assessing lumen stenosis degree. • 3D HR-MRI can accurately assess the degree of intracranial atherosclerotic stenosis. [ABSTRACT FROM AUTHOR]

FeCrCo magnetic films are suitable candidates for use as magnetic code disk materials in high-accuracy magnetic encoders. The performance and material uniformity of FeCrCo films are crucial for high-accuracy servo control of the encoder. However, enhancing coercivity and maintaining material uniformity while ensuring sufficient remanence in FeCrCo films pose challenges. Herein, Pt (t nm)/FeCrCo (100 nm) films were prepared via magnetron sputtering and subsequent vacuum annealing. The remanence of the FeCrCo (100 nm) monolayer film is 520 emu/cm3, with a coercivity of only 380 Oe. However, after using Pt as the buffer layer, the remanence of Pt (1 nm)/FeCrCo (100 nm) and Pt (2 nm)/FeCrCo (100 nm) films is 320 emu/cm3 and 250 emu/cm3 respectively, while the coercivity increases to 520 Oe and 625 Oe respectively, representing improvements of 37 % and 65 %. This significant increase in coercivity is achieved with the remanence still meeting the performance requirements of the magnetic code disk. High-resolution transmission electron microscopy (HRTEM) analysis reveals that diffused Pt atoms can facilitate the formation of a small amount of non-magnetic γ-FeCrCo phase, which has a pinning effect on magnetic domain walls, thus significantly increasing the coercivity of the FeCrCo film. Moreover, since the γ-FeCrCo phase and the α-FeCrCo phase have similar crystal lattices, material uniformity can be maintained, which is beneficial for ensuring the uniformity of output signals of the code disk with small magnetic pole pitches. [Display omitted] [ABSTRACT FROM AUTHOR]

The optical and structural properties of InGaN/GaN multi-quantum wells (MQWs) with different thicknesses of low temperature grown GaN cap layers are investigated. It is found that the MQW emission energy red-shifts and the peak intensity decreases with increasing GaN cap layer thickness, which may be partly caused by increased floating indium atoms accumulated at quantum well (QW) surface. They will result in the increased interface roughness, higher defect density, and even lead to a thermal degradation of QW layers. An extra growth interruption introduced before the growth of GaN cap layer can help with evaporating the floating indium atoms, and therefore is an effective method to improve the optical properties of high indium content InGaN/GaN MQWs. [ABSTRACT FROM AUTHOR]

The leakage mechanism of large size GaN p–i–n diodes is studied, and the possible reasons are analyzed. It is found that (i) the leakage current of most diode chips is not proportional to their area, and the leakage problem deteriorates seriously when the size of the device increases; (ii) the open circuit voltage of the photovoltaic device decreases with the increasing leakage current of GaN diodes; and (iii) low density nanotubes are detected in larger size GaN diodes, which is one of the important reasons for the large leakage of large size GaN diodes. [ABSTRACT FROM AUTHOR]

High-entropy alloy is an alloy design concept without a principal component. This concept not only refers to the complexity of alloy compositions but also means that when the high-entropy alloy transits from a high-energy state to low-energy state, there will be more intermediate metastable states. Corresponding to different states are the changes in the degree and manner of order in the microstructure. In this study, we used machine learning to combine elemental characteristics with long-term ordering and established 87% of prediction accuracy. This data-driven method can correlate elemental characteristics and metastable states and accelerate the discovery of potential compositions. [ABSTRACT FROM AUTHOR]

The significant effect of the thickness of Ni film on the performance of the Ohmic contact of Ni/Au to p-GaN is studied. The Ni/Au metal films with thickness of 15/50 nm on p-GaN led to better electrical characteristics, showing a lower specific contact resistivity after annealing in the presence of oxygen. Both the formation of a NiO layer and the evolution of metal structure on the sample surface and at the interface with p-GaN were checked by transmission electron microscopy and energy-dispersive x-ray spectroscopy. The experimental results indicate that a too thin Ni film cannot form enough NiO to decrease the barrier height and get Ohmic contact to p-GaN, while a too thick Ni film will transform into too thick NiO cover on the sample surface and thus will also deteriorate the electrical conductivity of sample. [ABSTRACT FROM AUTHOR]

In Mn50Ni41-xSn9Cox ribbons, the exchange bias field is very sensitive to the Co content. Based on both theoretical and experimental studies, it has been found that with increasing Co content, the pinned phase (ferromagnetic phase) remains almost unchanged while the pinning phase is changed from a canonical spin glass to a cluster spin glass and finally to a ferromagnetic phase. Changing the Co content in Mn50Ni41-xSn9Cox alloys has been proven to be an effective way of tuning the magnetic anisotropy and the phase structure of the pinning phase. With different Co contents, a continuous tuning of the exchange bias field from 345 Oe to 3154 Oe is realized. [ABSTRACT FROM AUTHOR]

The influence of unintentionally doped carbon impurities on electrical resistivity and yellow luminescence (YL) of low-temperature (LT) grown Mg doped GaN films is investigated. It is found that the resistivity of Mg doped GaN films are closely related to the residual carbon impurity concentration, which may be attributed to the compensation effect of carbon impurities. The carbon impurity may preferentially form deep donor complex CN-ON resulting from its relatively low formation energy. This complex is an effective compensate center for MgGa acceptors as well as inducing YL in photoluminescence spectra. Thus, the low resistivity LT grown p-type GaN films can be obtained only when the residual carbon impurity concentration is sufficiently low, which can explain why LT P-GaN films with lower resistivity were obtained more easily when relatively higher pressure, temperature, or NH3/TMGa flow rate ratio were used in the LT grown Mg doped GaN films reported in earlier reports. [ABSTRACT FROM AUTHOR]

In metallic glasses (MGs), a clear correlation has been established between plasticity and the Poisson's ratio. Such a correlation between the two distinctive macroscopic mechanical properties is challenging to explain from a microstructure perspective. We studied the microstructural origin of the Poisson's ratio and plasticity criterion in various MGs and find a correlation between the relative concentration of flow units and Poisson's ratio: the MGs with higher concentration of flow units show a larger Poisson's ratio and better plasticity. We have explained the empirical correlation between ductility and the Poisson's ratio based on microscopic flow units in MGs. [ABSTRACT FROM AUTHOR]

A set of dedicated marker samples consisting of fine-grain graphite as substrate, an interlayer of 0.2–0.4 μm molybdenum (Mo) employed as marker, and a 5–10 μm thick carbon (C) marker layer on top were installed in Wendelstein 7-X (W7-X) to investigate locally the C erosion and deposition. In this study, a set of five individual marker tiles, installed in a vertical divertor element of the test divertor unit in half-module 50, and exposed to about 40 min of plasma predominant in the standard magnetic divertor configuration in the first year of divertor operation in W7-X (OP1.2A), were retrieved from the vessel for post-mortem analysis. Picosecond laser induced breakdown spectroscopy (ps-LIBS) was applied on these marker tiles in order to determine the local erosion/deposition pattern caused by plasma impact. The general erosion/deposition pattern on the vertical target element was studied with the aid of depth-profiling by Mo line emission due to ps-LIBS with the number of applied laser pulses (355 nm, 2.3 J cm−2, 35 ps) at one probing location. Several potential asymmetry factors which avoid a perfect layer-by-layer ablation process in the laser ablations are proposed and discussed when a rough layered structure sample with a rough surface is analysed by the ps-LIBS technique. Thereby, a simulation model was developed to correct the measurement error of the ps-LIBS method caused by the non-perfect rectangle profile of the applied laser beam. The depth resolution of the applied ps-LIBS system was determined by quantification of the laser ablation rates of the different layers and the C substrate which were measured utilising profilometry and cross comparison with the thicknesses of the C and Mo marker layers determined by a combined focused ion beam and scanning electron microscopy technique. For the first time, the erosion/deposition pattern on the vertical target was mapped and quantified by ps-LIBS technique. A relatively wide net erosion zone with a poloidal extend of about 200 mm was identified which can be correlated to the main particle interaction zone at the magnetic strike-line of the dominantly applied standard magnetic divertor configuration. At the position of peak erosion, not only 7.6 × 1019 C atoms/cm2 but also 2 × 1018 Mo atoms/cm2 which results can be extrapolated to total 15 × 1019 C atoms/cm2, were eroded due to plasma fuel particle (H, He) and impurity (O, C) ion impact. [ABSTRACT FROM AUTHOR]

Resistance test is a classical method used to study ship performance. In this study, the uncertainty of large-scale ship model resistance test in actual seas is analyzed. Considering the difference between these trials and traditional test in towing tanks, this study first uses the ITTC 2014 procedure based on GUM to calculate the systematic error in the test. The parameters that affect the test accuracy are also estimated. Then, the program based on the Monte Carlo method is verified, and the differences between the two methods are compared. In this study, the uncertainty sources in the test are quantitatively analyzed, and the results will be helpful for improving the ship model test scheme in actual seas. [ABSTRACT FROM AUTHOR]

The effect of quantum barrier (QB) thickness on performances of InGaN/GaN multiple-quantum-well light-emitting diodes (MQW LEDs) with relatively large barrier layer thicknesses has been investigated. It is found that the density and averaged size of V-defects increases with QB thickness, resulting in larger reverse- and forward-bias current in LEDs. Electroluminescence measurement shows that LED with thinner QB has higher internal quantum efficiency but lower efficiency droop-onset current density, which should be ascribed to the faster saturation of carrier leakage into V-defects. Correspondingly, above the droop-onset current density, severer Auger recombination and carrier overflow are induced by higher carrier density due to the less V-defect related carrier leakage, leading to the more serious droop phenomenon in LEDs with thinner QB. [ABSTRACT FROM AUTHOR]

• New experimental data on the horizontal plug to slug transition flow is reported. • Drift flux analysis is performed in horizontal plug to slug transition flow. • Good agreement between current data against existing models and correlations was confirmed. A thorough understanding of the behaviour of the transition from plug to slug flow is imperative based on the fact that the transition can trigger an abrupt radial pressure variation. This can bring about major vibrations to the pipeline and also lead to big differences in pressure gradient and wall temperature. Unfortunately, the transition from plug to slug flow is poorly understood due to the scarce availability of experimental data. Furthermore, a considerable amount of research on the transition from plug to slug flow in the literature is based on an air–water system. In this work, the transition behaviour from plug to slug flow in a horizontal pipeline was experimentally investigated using electrical capacitance tomography (ECT). Working fluids are air–silicone oil. The work was carried out over a range of liquid and gas superficial velocities of 0.05–0.47 m/s and 0.05–4.7 m/s, respectively. Wave growth and wave characteristics mechanisms were observed to be responsible for the transition from plug to slug flow based on the obtained experimental results. Both liquid and gas superficial velocities have a major influence also on these mechanisms. The drift flux parameters for the transition from plug to slug flow was determined. A reasonably good agreement was observed from the comparison between present experimental data against hitherto published empirical models and correlations. [ABSTRACT FROM AUTHOR]

The leaching behavior of hemimorphite in neutral solution (NH4 +-Cl--H2O) was investigated at high temperature (T > 100 °C) under a range of experimental conditions. Thermodynamic calculations indicate that the tendency of dehydration of silica gel is significantly enhanced with the increasing temperature. It was shown that the temperature, ammonium chloride concentration, or L/S ratio increased resulted in greater leaching efficiency. The following optimized leaching conditions were obtained: stirrer speed 400r/min, NH4Cl concentration 5.5M, L/S ratio 9mL/g at 160 oC for 3h. Under these optimized conditions, the average leaching yield of zinc was 97.82%. The silicon was converted to quartz and remained in the residue. This process can be used to dispose willemite and hemimorphite as it solves the problem of silica gel dehydration. [ABSTRACT FROM AUTHOR]

By adopting one imidazole multi-carboxylate ligand, 2-(3-carboxylphenyl)-1H-imidazole-4,5-dicarboxylic acid (m-CPhH4IDC) and one N-containg ligand, 2,2′-bipyridine (2,2′-Bipy) to react with Cd(NO3)2, under solvothermal condition, a two-dimensional metal-organic framework, {[Cd6(m-CPhHIDC)4(2,2′-Bipy)6] · 4H2O}n (I) has been sucessfully constructed. The structure has been determined by single-crystal X-ray diffraction analysis (CIF files CCDC no. 1480230) and further characterized by elemental analyses, IR spectra, and thermogravimetric analysis. MOF I exhibits a rare (3,4)-connected 2D structure bearing two kinds of organic ligands. According to the crystal data, the coordination ability and mode of the imidazole multi-carboxylate ligand are discussed. Furthermore, the thermal stability and solid-state photoluminescent properties of MOF I have been investigated. [ABSTRACT FROM AUTHOR]

An ancient, large-scale, river-damming landslide in Koushan Village, Wenchuan County, Sichuan Province, located in the upstream of the Minjiang River, had a large influence on the valley evolution of the Minjiang River. Our investigation estimated that the landslide volume was 1.5 billion m3. The elevation of the scarp is 2700 m, 1000 m above the present accumulation of the landslide. The residual dam is comparatively complete, with calcium cementation. The highest point of the dam is 221 m higher than the Minjiang River. The dammed lake extends for 38 km and reaches as far as Maoxian County. The investigation results indicate that an earthquake was probably the main cause of the landslide. The damming mechanism was associated with rock avalanches. These rock avalanches subsequently blocked the Minjiang River. The dam exhibits multi-stage breaching, which can be divided into overflow erosion and rapid cutting stages. The 14C dating results indicate that the landslide occurred at least 22,000 years ago and that the dam was breached at least 11,700 years ago. [ABSTRACT FROM AUTHOR]

Aims: Porcine circovirus type 2 (PCV2) can cause postweaning, multisystemic wasting syndrome in pigs, which leads to enormous losses in the swine industry worldwide. Here, a genetically engineered Lactococcus strain expressing the main protective antigen of PCV2, the Cap protein, was developed to act against PCV2 infection as an oral vaccine. Methods and Results: Expression of the Cap protein was confirmed via western blot, ELISA and fluorescence microscopy. Over 90% of the recombinant pAMJ399‐Cap/MG1363 survived a simulated gastrointestinal transit. It also survived the murine intestinal tract for at least 11 days. Then, the safety and immunogenicity of pAMJ399‐Cap/MG1363 in orally immunized mice was evaluated. The levels of the sIgA, IgG and cytokines (IL‐4 and IFN‐γ) obtained from the mice immunized with pAMJ399‐Cap/MG1363 were significantly higher than those in the control groups. Conclusions: pAMJ399‐Cap/MG1363 can survive in the gastrointestinal transit and effectively induce mucosal, cellular and humoral immune response against PCV2 infection via oral administration. Significance and Impact of the Study: This study demonstrates the potential of the genetically engineered Lactococcus lactis as a candidate for an oral vaccine against PCV2. [ABSTRACT FROM AUTHOR]

The autoionization mechanisms of dense nP3/2 (n = 20–97) Rydberg gases of 87Rb atoms in the spontaneous evolution were investigated for the first time. By observing the characteristic time of the electrons generated through autoionization process, the dependence of autoionization mechanisms (black‐body radiation, electron–Rydberg collision, and Penning ionization) on the principal quantum number n of initial nP states was demonstrated. The dependence on the number n in nP Rydberg atoms is similar to those in nD Rydberg atoms. [ABSTRACT FROM AUTHOR]

A new polynuclear silver complex Ag6(W2O5)(Cid)2 based on citric acid is obtained by hydrothermal method and studied by single crystal X-ray diffraction compound The compound crystallizes in triclinic space group P , Z = 1. The structure solution is complicated by two component non-merohedral twinning. The structure feature is a 3D framework containing 1D infinite [Ag]∞ chains. Ag atoms are connected by metal–metal bonding interaction with the Ag–Ag distances of 2.849(3)–3.218(2) Å. [ABSTRACT FROM AUTHOR]

Performance of InGaN-based laser diodes (LDs) with different Mg concentrations of electron blocking layer (EBL) is investigated by simulation and experimental methods. It is found from the simulation results that the threshold current decreases and slope efficiency increases, when the Mg concentration of EBL increases from 2 × 1018 to 6 × 1019 cm−3; it is attributed to the suppression of the leakage of electrons and the enhancement of the injection of holes due to the variation of potential barrier for them as the increase of Mg concentration of EBL. These simulation results agree well with the experimental ones, when the Mg concentration of EBL is lower than 7.5 × 1018 cm−3. However, it deteriorates when the Mg concentration increases to 1.2 × 1019 cm−3. It may be due to the increase of the absorption loss of LDs. [ABSTRACT FROM AUTHOR]

We have investigated the effect of light Si-doping on the optical properties of high quality GaN films with the method of low temperature photoluminescence. It is found that the peak (Ix) at 3.473 eV always appears in the photoluminescence spectra of lightly Si-doped GaN. The relative intensity of peak Ix to heavy-hole free exciton peak increases linearly with the increasing concentration of Si doping, providing a strong support to the assignment that Ix originates from inelastic scattering of free excitons by Si donors. In addition, a rarely reported peak (Px) at 3.365 eV can only be clearly observed in the PL spectrum of unintentionally doped GaN sample. Its intensity is found to reduce dramatically with the decrease of residual carbon concentration based on the secondary ion mass spectrometry analysis. Px is attributed to the excitons bound to carbon-related complex defects. [ABSTRACT FROM AUTHOR]

The spectral responses of back-illuminated p-i-n AlGaN ultraviolet photodetector under different bias voltage are investigated. The device structure is composed of p-GaN/p-Al0.3Ga0.7N/i-Al0.3Ga0.7N/n-Al0.6Ga0.4N and Ohmic contacts, where the p-GaN layer is very thin. There are two peaks in the spectral response of photocurrent located at 350 and 290 nm, respectively. It is found that in some devices the relative intensity and phase of these two peaks may change strongly with applied forward bias. A detailed analysis suggests that the possible Schottky-type-like behavior of metal and p-GaN contact and an unsatisfactory doping of p-GaN and p-AlGaN are responsible for the abnormal phenomenon. [ABSTRACT FROM AUTHOR]

It is studied whether there is any regular relationship between the yellow luminescence band and electron mobility of n-type GaN. For a series of GaN samples grown with the same Si doping, it is found that the electron mobility decreases with an increase of relative intensity of yellow luminescence, accompanied by an increase of edge dislocation density. Further research indicates that it is acceptors introduced by edge dislocations which lead to the concomitant changes of yellow luminescence and electron mobility. Similar changes are induced by Si doping in the n-type GaN samples with relatively low edge dislocation density. However, the relationship between the yellow luminescence and electron mobility of n-type GaN is not a simple one. A light Si doping may simultaneously increase yellow luminescence and electron mobility when Si doping plays a dominant role in reducing the carrier scattering. This means that even the intensity of yellow luminescence is often used as an indicator of material quality for GaN, it does not have any monotonous correlation with the electron mobility of GaN. [ABSTRACT FROM AUTHOR]

We investigate the quasistatic magnetic hysteresis of ferromagnetic thin films grown on a vicinal substrate, using Monte Carlo simulations within a two-dimensional XY model. Intrinsic in-plane anisotropy is assigned to surface sites according to their local symmetry. The simulated hysteresis loops show a strong anisotropy: the coercive field is the largest when the external field is along the step direction and vanishes when the external field is perpendicular to the step direction. In general, the coercivity increases with increasing step density, but displays a more complex dependence on film thickness. The simulations also suggest that the mechanism for the magnetization reversal is coherent rotation. These results are in good agreement with experiments. [ABSTRACT FROM AUTHOR]

Finding new luminescent materials is always a meaningful goal in the field of photoelectricity studies. Herein, a new diphosphate compound Ba2LiGa(P2O7)2 (BLGP) was prepared using a high-temperature flux method. It displays an anionic chain structure of [LiGa(P2O7)2]∞, constructed from P2O7, LiO5 and GaO6 polyhedra. The Ba2+ ions are distributed in the voids between the [LiGa(P2O7)2]∞ chains, bonding them and maintaining charge balance. To test its potential as a luminescent host, Eu3+ doped phosphors BLGP:xEu3+ (x = 0.05, 0.10, 0.15, 0.20, 0.25 and 0.30) were synthesized and studied in detail. Upon 394 nm light irradiation, BLGP:xEu3+ showed bright orange emission with a dominant peak at 595 nm due to the 5D0 → 7F1 transition of Eu3+. The optimal doping amount of Eu3+ is 0.20, and the internal quantum efficiency of the phosphor B1.8LGP:0.2Eu3+ was determined to be 67%. The temperature quenching behavior of B1.8LGP:0.2Eu3+ was studied, suggesting that the photoluminescence (PL) intensity decreased to about 50% at 450 K due to thermal quenching. All these features show that this compound is a good luminescent host material for Eu3+ activators. [ABSTRACT FROM AUTHOR]

Ti-Al based alloys have been widely used in the aeronautics and aerospace. Adding alloying element Zr can significantly improve their high-temperature endurance and corrosion resistance. To investigate the influence of the addition of element Zr on the properties of the Ti-Al system, ab initio calculations and the CALPHAD (CALculation of PHAse Diagrams) method were used to evaluate the Ti-Al-Zr ternary system. Ab initio calculations were carried out to calculate the formation enthalpies of intermetallic compounds and end-members. CALPHAD approach was employed to optimize the thermodynamic parameters based on experiments. The experimental data of phase equilibria at 1073, 1273, 1473, and 1573 K, as well as a vertical section of the Ti3Al-Ti + 5 wt.% Zr were used to assess this system. The thermodynamic parameters of the binary Ti-Al, Al-Zr and Ti-Zr systems were acquired from recent assessments, and the ternary ones were evaluated in the present work. The Ti-Al-Zr ternary dataset has been established and the calculated results are in close agreement with the experimental data on both thermodynamics and phase equilibria. [ABSTRACT FROM AUTHOR]

Abstract To uncover the physical correlation between intrinsic structural heterogeneity and mechanical properties of metallic glasses, we performed high-pressure torsion (HPT) to tailor their microstructure with a rejuvenated state. Nanoindentation results show that the change of mechanical properties results from the convolution of the intrinsic thermal activation process and the structural inhomogeneity in the glassy phase. The spatial heterogeneity induced by severe plastic deformation can markedly operate to reduce the energy barrier for shear transformation zone (STZ) activation and increase the number of STZ events during tensile testing to accommodate the plastic strain, leading to a brittle-to-ductile transition. We highlight that by properly controlling the distribution of structural heterogeneities, one can purposely tune the mechanical performance of metallic glasses. [ABSTRACT FROM AUTHOR]

Objective: To examine whether maternal aspirin use during pregnancy is associated with childhood blood pressure.Design/setting: A secondary analysis of the Collaborative Perinatal Project, a prospective cohort study including 12 US academic medical centres between 1959 and 1976.Population: Singleton births among women with detailed medication information.Methods: We carried out linear and multivariate logistic regression analysis to assess the associations between maternal aspirin exposure and childhood blood pressure at age 7 years.Main Outcome Measures: Offspring blood pressure at age 7 years.Results: A total of 15 793 women were exposed to aspirin 4 weeks before the last menstrual period or during pregnancy. In utero aspirin exposure may be associated with an 11% (95% CI 0.85- 0.93) and a 20% (95% CI 0.76-0.84) reduced risk of having high systolic blood pressure (SBP) and diastolic blood pressure (DBP) at 7 years of age, and a mean decrease of 0.62 mmHg for SBP and 1.04 mmHg for DBP at 7 years of age. Compared with children born to mothers without aspirin exposure, those whose mothers were exposed to aspirin for at least 7 days during pregnancy had approximately 10% and 27% reduced risk of high SBP and DBP, respectively, and a mean reduction of 0.61 and 1.27 mmHg in SBP and DBP at 7 years of age. The earlier the aspirin exposure occurred during pregnancy, the lower the risk of childhood high blood pressure.Conclusion: In utero exposure to aspirin may have long-term benefits for childhood blood pressure.Tweetable Abstract: Maternal aspirin exposure might decrease the risk of childhood blood pressure. [ABSTRACT FROM AUTHOR]

The article offers a study that examine the quality of life (QoL) in children with osteogenesis imperfecta (OI). Topics discussed include the Osteogenesis imperfecta (OI) is hereditary disease characterized by multiple fragility fractures and progressive skeletal deformities, mentions the validated questionnaire of PedsQL to evaluate the health-related quality of life (HRQoL) of children and adolescents with OI, and information on the patients with severe OI had poorer HRQoL scores.

Two new coordination polymers Co(C9H7N7)(SO4)(H2O) (I) and Cd(C9H6N7)2·H2O (II), where C9H7N7 is 4-(5-(1H-1,2,4-triazol-1-ylmethyl)-1,2,4-triazol-3-yl)pyridine, are synthesized through hydrothermal reactions and structurally determined by single-crystal X-ray diffraction analyses. The results reveal that compound I belongs to the triclinic space group P-1 with a 1-D chain structure, whereas compound II belongs to the monoclinic space group C2 with a 2D layer structure. Hydrogen bonds play an important role in the construction of 3D structure of the two compounds. [ABSTRACT FROM AUTHOR]

Through application of energy-balance arguments to the crossed-beam reaction Ba(1S0)+HI(X 1Σ+) →BaI(X 2Σ+) +H(2S1/2), a lower limit for the BaI bond dissociation energy is determined to be D00(BaI) >=76.8±1.7 kcal/mol (3.33±0.07 eV). Based on the upper bound of D00(BaI) ≲78.5±0.5 kcal/mol, as determined from earlier predissociation studies [M. A. Johnson, J. Allison, and R. N. Zare, J. Chem. Phys. 85, 5723 (1986)], we recommend a BaI bond strength of 77.7±2.0 kcal/mol (3.37±0.09 eV). This dissociation energy is more than 5 kcal/mol higher than the previously accepted value of D00(BaI) as derived from mass spectrometric measurements. [ABSTRACT FROM AUTHOR]

The skin made of micro floating raft arrays is a novel method in drag reduction engineering, the study of nonlinear boundary layer stability of flow over the skin is necessary. The weakly nonlinear stability theory is applied to flow over the skin. The weakly nonlinear stability problem of flow over the skin is solved for the first time. The weakly nonlinear flow stability characteristics of skin are analyzed. The results show that increase in the stiffness and damping ratios intensifies the distorted velocity of the Tollmien–Schlichting waves (TSW) but decrease the distorted velocity of travelling-wave flutter (TWF). Reducing the interval and the middle mass of the micro floating raft element can lead to a similar influence on the distorted velocity. The nonlinearity does not change the objective law of the effect of skin's parameters on stability in the boundary layer. The skin can effectively improve the weakly nonlinear stability of the Tollmien–Schlichting waves: the skin with appropriate parameters lightens the velocity distortedness and reduces the perturbation nonlinear growth rate. The better control ability of skin on nonlinear flow stability also proves the potential in drag reduction. [ABSTRACT FROM AUTHOR]

Silicon carbide (SiC), as one of the most favorite wide band gap semiconductor materials, is often applied in power electronics nowadays. The reliability of SiC packages, however, hasn't been sufficiently investigated yet, and unexploited potentials are still expected. One critical impact parameter is the geometric chip design, from which its thickness is the most easily accessible feature. In this paper, finite element simulations are performed to investigate the influence of SiC chip thickness on the power cycling capability based on a "standard" power electronics assembly concept. The results show a potential increase of the power cycling lifetime for solder fatigue by 7 times and bond wire lift-off by 8 times when decreasing the SiC chip thickness from 350 μm to 50 μm. On the other hand, by decreasing the chip thickness, the risk for chip fracture increases due to increasing tensile stresses in the chip surface. • Investigation of influence of SiC chip thickness on power cycling capability based on a "standard" power electronic assembly via FE-modelling and advanced post-processing method • Understanding the influence of chip thickness variation on typical failure mechanisms in power cycling test • Quantitative assessment of power cycling lifetime for SiC and Si chips with different thicknesses regarding solder fatigue and bond wire lift-off • Thinning SiC chip to 50 μm results in a better power cycling capability than 200 μm Si chip [ABSTRACT FROM AUTHOR]

The performance of ultraviolet (UV) laser diodes (LDs) with a low Al mole fraction AlGaN cladding layer was investigated by varying the thicknesses of the waveguide layer. It is found that (1) the loss of carriers in the waveguide layer is much larger than that in blue or green LDs due to the shallower quantum well and consequently a weaker carrier confinement of UV lasers. (2) Carrier loss in the waveguide layer can be suppressed by using a thinner waveguide layer. Therefore, the threshold current of LDs can be reduced. (3) The ultraviolet GaN/AlGaN single quantum well laser diodes lasing at 366 nm are fabricated by using relatively thin AlGaN waveguide layers and low Al mole fraction AlGaN cladding layers. [ABSTRACT FROM AUTHOR]